Two-Dimensional Temporal Clustering Analysis for Patients with Epilepsy: Detecting Epilepsy-Related Information in EEG-fMRI Concordant,Discordant and Spike-Less Patients

EEG acquired simultaneously with fMRI (EEG-fMRI) is a multimodal method that has shown promise in mapping the seizure onset zone in patients with focal epilepsy. However, there are many instances when this method is unsuccessful or not applicable, and other data driven fMRI methods may be utilized. One such method is the two-dimensional temporal clustering analysis (2dTCA). In this study we compared the classic EEG-fMRI and 2dTCA performance in mapping regions related to the seizure onset region in 18 focal epilepsy patients (12 presenting interictal epileptiform discharges (IEDs), during EEG-fMRI acquisition) with Engel I or II surgical outcome. Activation maps of both 2dTCA timing outputs (positive and negative histograms) and EEG detected IEDs were computed and compared to the region of epilepsy surgical resection. Patients were evaluated in three categories based on frequency of EEG detected spiking during the MRI. EEG-fMRI maps were concordant to the epilepsy region in 5/12 subjects, four with frequent IEDs on EEG. The 2dTCA was successful in mapping 13/18 patients including 3/6 with no IEDs detected (10/12 with IEDs detected). The epilepsy-related activities were successfully mapped by both methods in only 4/12 patients. This work suggests that the epilepsy-related information detected by each method may be different: while EEG-fMRI is more accurate in patients with high rather than lower numbers of EEG detected IEDs; 2dTCA can be useful in evaluating patients even when no concurrent EEG spikes are detected or EEG-fMRI is not effective. Therefore, our results support that 2dTCA might be an alternative for mapping epilepsy-related BOLD activity in negative EEG-fMRI (6/7 patients) and spike-less patients.     

青少年肌阵挛癫痫发作间期EEG-fMRI的研究

采用同步脑电与功能磁共振(Simultaneous electroencephalography-correlated functional magnetic resonance imaging,EEG-fMRI)技术,研究青少年肌阵挛癫痫患者发作间期痫样放电时脑部血氧水平依赖(Blood oxygen level-dependent,BOLD)信号变化。结果发现:双侧大脑半球的激活及失活信号变化普遍对称且各自独立存在,信号由枕顶至额区逐渐减少。阳性激活区有:楔叶、岛叶、额中部内侧、小脑中线两侧及丘脑。阴性激活区有:双侧额前部、顶部及扣带后回。由此推断:以棘慢复合波为表现形式的同步的神经元活动可能反映了丘脑皮层BOLD信号的激活,而失活区域反映了异常放电时的脑功能的静息状态;这类激活在神经元的活动(EEG)与fMRI结果之间有很好的对应关系;EEG-fMRI是研究脑功能状态有效的方式。     

On the relationship between slow cortical potentials and BOLD signal changes in humans.

This review summarizes experimental studies that investigated the relationship between DC-recorded slow event-related potentials (slow waves) of the electroencephalogram (EEG) and the hemodynamic BOLD response, as measured with functional magnetic resonance imaging (fMRI). Slow waves have been found to accompany a large number of cognitive processes in a systematic and topographically specific way, and have thus been successfully employed in psychophysiological experiments to dissociate cognitive functions by means of their slow wave topography. Recently, however, several independent studies, using different experimental paradigms, suggest the existence of another feature of slow waves, i.e., a close relationship with the fMRI BOLD response. Some of these studies found couplings between slow waves and BOLD signals in various brain regions, using simultaneous EEG-fMRI recordings. Others found similar task-related activation patterns of slow waves (i.e., scalp topographies) and BOLD responses (i.e., activated voxel profiles), as well as corresponding parametric increases of signal strength with increasing task difficulty. The close relationship between slow waves and BOLD responses reported here concerns a low frequency range of the EEG signal (<1 Hz) that has so far received less attention in studies on the correspondence between EEG and fMRI than the higher frequencies, and therefore adds to the various findings obtained at higher EEG frequencies. Implications for the use of slow waves for neuroscientific research are discussed.     

Hemodynamic Response Function (HRF) in Epilepsy Patients with Hippocampal Sclerosis and Focal Cortical Dysplasia

Simultaneous recording of electroencephalography and functional magnetic resonance imaging (EEG–fMRI) has recently been applied for mapping the hemodynamic changes related to epileptic activity. The aim of this study is to compare the hemodynamic response function (HRF) to epileptic spikes in patients with focal cortical dysplasia (FCD) and those with hippocampal sclerosis (HS). In EEG–fMRI studies, the HRF represents the temporal evolution of blood oxygenation level-dependent signal changes. Several studies demonstrated that amplitude and latency of the HRF are variable in patients with epilepsy. However, the consistency of HRF parameters with underlying brain pathology is unknown. In this study, we examined 14 patients with FCD and 12 with unilateral HS selected from our EEG–fMRI database and compared the amplitude and latency of the HRF peak. We analyzed (1) HRFs in peak activation clusters, (2) HRFs in peak deactivation clusters, and (3) the maximum absolute responses within the EEG spike field, activation or deactivation. We found that the HRF peak amplitude in deactivation clusters was larger in the HS group than in the FCD when the deactivation occurred in default mode network (DMN) regions. This result suggests that spikes in patients with HS affect the DMN more strongly than those with FCD. However, if we focus on the maximum absolute t-value in the spike field, there is no significant difference between the two groups. The current study indicates that it is not necessary to use different HRF models for EEG–fMRI studies in patients with FCD and HS.     

Non-REM sleep influences results of fMRI studies in epilepsy

Although negative blood oxygen level-dependent (BOLD) signal changes are very frequent findings in neuroimaging studies of neuronal networks underlying interictal epileptiform discharges (IEDs), the nature of negative BOLD effects in epilepsy remains unclear. To investigate the influence of sleep on BOLD responses to internal activity such as IED, hemodynamic changes associated with IED were analysed in sleep stages 1 and 2 in four children with focal epilepsies who underwent simultaneous EEG-fMRI recordings. There were significantly more voxels with negative BOLD responses and better fit of the expected with the real course of BOLD signal for the negative BOLD effect in sleep stage 2 compared to stage 1. Moreover, the increase in omega (12.0-14.0Hz) and delta (0.5-4.0Hz) power correlated with an increase in the number of deactivated voxels. This study indicates that the second stage of sleep seems to be associated with an increase in negative BOLD response to internal activity compared with sleep stage 1. An increase in inhibitory influences during sleep and decrease of sleep-associated, energy-consuming processes may be responsible for the described negative BOLD signal changes.     

Improving sensitivity of EEG-fMRI studies in epilepsy: the role of sleep-specific activity

Using simultaneous recordings of EEG and functional MRI (EEG-fMRI) in patients with focal epilepsy, recent studies have revealed insufficient sensitivity and a lack of correspondence between epileptic EEG foci and activation patterns in some patients. In this study of children with focal epilepsy, we explore whether sleep-specific activity (sleep spindles, k-complexes and vertex sharp waves) may increase the sensitivity of EEG-fMRI of interictal epileptiform discharges (IED). When considering the sleep-specific activity in a statistical model, it was possible to increase the statistical significance of the activated voxels inside of the expected source of the IED and to reduce the number of activated voxels outside of it. According to this study, it could be worthwhile to include sleep-specific activity into the model by analyzing EEG-fMRI data in epilepsy.     

Generalized Spike and Waves: Effect of Discharge Duration on Brain Networks as Revealed by BOLD fMRI

In the past decade, the possibility of combining recordings of EEG and functional MRI (EEG–fMRI), has brought a new insight into the brain network underlying generalized spike wave discharges (GSWD). Nevertheless, how GSWD duration influences this network is not fully understood. In this study we aim to investigate whether GSWD duration had a threshold (non-linear) and/or a linear effect on the amplitude of the associated BOLD changes in any brain regions. This could help in elucidating if there is an hemodynamic background supporting the differentiation between interictal and ictal events. We studied a population of 42 patients with idiopathic generalized epilepsies (IGE) who underwent resting-state EEG–fMRI recordings in three centres (London, UK; Modena, Italy; Rome, Italy), applying a parametric analysis of the GSWD duration. Patients were classified as having Childhood Absence epilepsy, Juvenile Absence Epilepsy, or Juvenile Myoclonic Epilepsy. At the population level linear GSWD duration-related BOLD signal changes were found in a network of brain regions: mainly BOLD increase in thalami and cerebral ventricles, and BOLD decrease in posterior cingulate, precuneus and bilateral parietal regions. No region of significant BOLD change was found in the group analysis for the non-linear effect of GSWD duration. To explore the possible effect of both the different IGE sub-syndromes and the different protocols and scanning equipment used in the study, a full-factorial ANOVA design was performed revealing no significant differences. These findings support the idea that the amplitude of the BOLD changes is linearly related to the GSWD duration with no universal threshold effect of spike and wave duration on the brain network supporting this activity.     

头皮脑电图继发双侧同步(癎)样放电的特点及其临床意义

目的:探讨局灶性癫(癎)患者头皮脑电图(EEG)上继发双侧同步(癎)样放电(SBSD)的表现特点及临床意义.方法:回顾性地分析自2002年3月至2006年3月,于我研究所接受治疗的所有局灶性癫(癎)患者的EEG资料,排除所有颞叶癫(癎),共32例患者的术前EEG上均存在SBSD表现.对这些患者的发作间期与发作期EEG结果进行分析研究.结果:32例患者中,SBSD起源于额区者20例,枕区者10例,顶区者2例.SBSD可表现为棘或尖波、棘慢复合波与快节律三种类型,以棘慢复合波最为常见,占63%.SBSD发作间期较为常见的特点是双侧存在时间差,SBSD始于EEG局灶性异常改变以及局限性慢波一侧;53%的病人发作期EEG表现为局灶性起源.结论:SBSD在局灶性癫(癎)患者中并不少见,而且以额叶最为常见.通过分析SBSD波形的各个特点,有助于判断SBSD原发灶侧别,并与全面性癫(癎)相鉴别,对癫(癎)外科的术前评估具有非常重要的临床意义.     

Cortical and subcortical correlates of electroencephalographic alpha rhythm modulation

Neural correlates of electroencephalographic (EEG) alpha rhythm are poorly understood. Here, we related EEG alpha rhythm in awake humans to blood-oxygen-level-dependent (BOLD) signal change determined by functional magnetic resonance imaging (fMRI). Topographical EEG was recorded simultaneously with fMRI during an open versus closed eyes and an auditory stimulation versus silence condition. EEG was separated into spatial components of maximal temporal independence using independent component analysis. Alpha component amplitudes and stimulus conditions served as general linear model regressors of the fMRI signal time course. In both paradigms, EEG alpha component amplitudes were associated with BOLD signal decreases in occipital areas, but not in thalamus, when a standard BOLD response curve (maximum effect at approximately 6 s) was assumed. The part of the alpha regressor independent of the protocol condition, however, revealed significant positive thalamic and mesencephalic correlations with a mean time delay of approximately 2.5 s between EEG and BOLD signals. The inverse relationship between EEG alpha amplitude and BOLD signals in primary and secondary visual areas suggests that widespread thalamocortical synchronization is associated with decreased brain metabolism. While the temporal relationship of this association is consistent with metabolic changes occurring simultaneously with changes in the alpha rhythm, sites in the medial thalamus and in the anterior midbrain were found to correlate with short time lag. Assuming a canonical hemodynamic response function, this finding is indicative of activity preceding the actual EEG change by some seconds.     

Negative BOLD effect on somato-motor inhibitory processing: An fMRI study

Inhibiting inappropriate behavior and thoughts in the current context is an essential ability for humans, but the neural mechanisms for response inhibitory processing are a matter of continuous debate. The aim of this event-related functional magnetic resonance imaging (fMRI) study was to evaluate the negative blood oxygen level dependent (BOLD) effect on inhibitory processing during go/no-go paradigms. Fifteen subjects performed two different types of somatosensory go/no-go paradigm: (1) button press and (2) count. Go and no-go stimuli were presented with an even probability. We observed a common negative activation during Movement No-go and Count No-go trials in the right SFG, corresponding to BA 8. These findings suggest that the right SFG region was responsible for the negative BOLD effect on inhibitory processing, which was independent of the required response mode. We hypothesized several possible explanations for the deactivation of the SFG during no-go trials.     

Localization Accuracy of Distributed Inverse Solutions for Electric and Magnetic Source Imaging of Interictal Epileptic Discharges in Patients with Focal Epilepsy

Distributed inverse solutions aim to realistically reconstruct the origin of interictal epileptic discharges (IEDs) from noninvasively recorded electroencephalography (EEG) and magnetoencephalography (MEG) signals. Our aim was to compare the performance of different distributed inverse solutions in localizing IEDs: coherent maximum entropy on the mean (cMEM), hierarchical Bayesian implementations of independent identically distributed sources (IID, minimum norm prior) and spatially coherent sources (COH, spatial smoothness prior). Source maxima (i.e., the vertex with the maximum source amplitude) of IEDs in 14 EEG and 19 MEG studies from 15 patients with focal epilepsy were analyzed. We visually compared their concordance with intracranial EEG (iEEG) based on 17 cortical regions of interest and their spatial dispersion around source maxima. Magnetic source imaging (MSI) maxima from cMEM were most often confirmed by iEEG (cMEM: 14/19, COH: 9/19, IID: 8/19 studies). COH electric source imaging (ESI) maxima co-localized best with iEEG (cMEM: 8/14, COH: 11/14, IID: 10/14 studies). In addition, cMEM was less spatially spread than COH and IID for ESI and MSI (p < 0.001 Bonferroni-corrected post hoc t test). Highest positive predictive values for cortical regions with IEDs in iEEG could be obtained with cMEM for MSI and with COH for ESI. Additional realistic EEG/MEG simulations confirmed our findings. Accurate spatially extended sources, as found in cMEM (ESI and MSI) and COH (ESI) are desirable for source imaging of IEDs because this might influence surgical decision. Our simulations suggest that COH and IID overestimate the spatial extent of the generators compared to cMEM.     

Wavelet Analysis as a Tool for Investigating Movement-Related Cortical Oscillations in EEG-fMRI Coregistration

Electroencephalography combined with functional magnetic resonance imaging (EEG-fMRI) identifies blood oxygenation level dependent (BOLD) signal changes associated with physiological and pathological EEG events. In this study we used EEG-fMRI to determine the possible correlation between topographical movement-related EEG changes in brain oscillatory activity recorded from EEG electrodes over the scalp and fMRI cortical responses in motor areas during finger movement. Thirty-two channels of EEG were recorded in 12 subjects during eyes-closed condition inside a three T magnetic resonance (MR) scanner using an MR-compatible EEG recording system. Off-line MRI artifact subtraction software was applied to obtain continuous EEG data during fMRI acquisition. For EEG data analysis we used a time–frequency approach to measure time by varying the energy in a signal at a given frequency band by the convolution of the EEG signal with a wavelet family in the alpha and beta bands. The correlation between the BOLD signal associated with the EEG regressor provides that sensory motor region is a source of the EEG. We conclude that combined EEG-fMRI can be used to investigate movement-related oscillations of the human brain inside an MRI scanner and wavelet analysis adds further details on the EEG changes. The movement-related changes in the EEG signals are useful to identify the brain activation sources responsible for BOLD-signal changes.     

EEG and fMRI Coregistration to Investigate the Cortical Oscillatory Activities During Finger Movement

Electroencephalography combined with functional magnetic resonance imaging (EEG-fMRI) may be used to identify blood oxygenation level dependent (BOLD) signal changes associated with physiological and pathological EEG event. In this study we used EEG-fMRI to determine the possible correlation between topographical movement-related EEG changes in brain oscillatory activity recorded from EEG electrodes over the scalp and fMRI-BOLD cortical responses in motor areas during finger movement. Thirty-two channels of EEG were recorded in 9 subjects during eyes-open condition inside a 1.5 T magnetic resonance (MR) scanner using a MR-compatible EEG recording system. Off-line MRI artifact subtraction software was applied to obtain continuous EEG data during␣fMRI acquisition. For EEG data analysis we used the event-related-synchronization/desynchronization (ERS/ERD) approach to investigate where movement-related decreases in alpha and beta power are located. For image statistical analysis we used a general linear model (GLM) approach. There was a significant correlation between the positive-negative ratio of BOLD signal peaks and ERD values in the electrodes over the region of activation. We conclude that combined EEG-fMRI may be used to investigate movement-related oscillations of the human brain inside an MRI scanner and the movement-related changes in the EMG or EEG signals are useful to identify the brain activation sources responsible for BOLD-signal changes.     

Brain areas activated in fMRI during self-regulation of slow cortical potentials (SCPs)

In humans, surface-negative slow cortical potentials (SCPs) originating in the apical dendritic layers of the neocortex reflect synchronized depolarization of large groups of neuronal assemblies. They are recorded during states of behavioural or cognitive preparation and during motivational states of apprehension and fear. Surface positive SCPs are thought to indicate reduction of cortical excitation of the underlying neural networks and appear during behavioural inhibition and motivational inertia (e.g. satiety). SCPs at the cortical surface constitute summated population activity of local field potentials (LFPs). SCPs and LFPs may share identical neural substrates. In this study the relationship between negative and positive SCPs and changes in the BOLD signal of the fMRI were examined in ten subjects who were trained to successfully self-regulate their SCPs. FMRI revealed that the generation of negativity (increased cortical excitation) was accompanied by widespread activation in central, pre-frontal, and parietal brain regions as well as the basal ganglia. Positivity (decreased cortical excitation) was associated with widespread deactivations in several cortical sites as well as some activation, primarily in frontal and parietal structures as well as insula and putamen. Regression analyses revealed that cortical positivity was predicted with high accuracy by pallidum and putamen activation and supplementary motor area (SMA) and motor cortex deactivation, while differentiation between cortical negativity and positivity was revealed primarily in parahippocampal regions. These data suggest that negative and positive electrocortical potential shifts in the EEG are related to distinct differences in cerebral activation detected by fMRI and support animal studies showing parallel activations in fMRI and neuroelectric recordings.Supported by the Deutsche Forschungsgemeinschaft (DFG)     

Convergence of fMRI and ERP measures of emotional face processing in combat‐exposed U. S. military veterans

The late positive potential (LPP) and fMRI blood‐oxygen‐level dependent (BOLD) activity can provide complementary measures of the processing of affective and social stimuli. Separate lines of research using these measures have often employed the same stimuli, paradigms, and samples; however, there remains relatively little understanding of the way in which individual differences in one of these measures relates to the other, and all prior research has been conducted in psychiatrically healthy samples and using emotional scenes (not faces). Here, 32 combat‐exposed U. S. military veterans with varying levels of posttraumatic stress symptomatology viewed affective social stimuli (angry, fearful, and happy faces) and geometric shapes during separate EEG and fMRI BOLD recordings. Temporospatial principal component analysis was used to quantify the face‐elicited LPP in a data‐driven manner, prior to conducting whole‐brain correlations between resulting positivities and fMRI BOLD elicited by faces. Participants with larger positivities to fearful faces (> shapes) showed increased activation in the amygdala; larger positivities to angry and happy faces (> shapes) were associated with increased BOLD activation in the posterior fusiform gyrus and inferior temporal gyrus, respectively. Across all face types, larger positivities were associated with increased activation in the fusiform “face” area. Correlations using mean area amplitude LPPs showed an association with increased activation in the anterior insula for angry faces (> shapes). LPP‐BOLD associations were not moderated by PTSD. Findings provide the first evidence of correspondence between face‐elicited LPP and BOLD activation across a range of (normal to disordered) psychiatric health.     

Correspondence of Visual Evoked Potentials with FMRI Signals in Human Visual Cortex

Functional magnetic resonance imaging (FMRI) and event related potentials (ERPs) are tools that can be used to image brain activity with relatively good spatial and temporal resolution, respectively. Utilizing both of these methods is therefore desirable in neuroimaging studies to explore the spatio-temporal characteristics of brain function. While several studies have investigated the relationship between EEG and positive (+) BOLD (activation), little is known about the relationship between EEG signals and negative (−) BOLD (deactivation) responses. In this study, we used a visual stimuli designed to shift cortical activity from anterior to posterior regions of the visual cortex. Using EEG and FMRI, we investigated how shifts in +BOLD and −BOLD location were correlated to shifts in the N75 and P100 visual evoked potential (VEP) dipolar sources. The results show that the N75 dipole along with +BOLD, were indeed shifted from posterior to anterior regions of the visual cortex. The P100 VEP component, along with the −BOLD were not shifted to the same extent, indicating that N75 is better correlated to +BOLD than to −BOLD. These findings indicate how different components of the EEG signal are related to the positive and negative BOLD responses, which may aid in interpreting the relationship between visually evoked EEG and FMRI signals. An erratum to this article can be found at     

Activation and deactivation in response to visual stimulation in the occipital cortex of 6-month-old human infants

In an infant's developing cortex, the explanation for the mechanisms underlying the activations and deactivations in response to visual stimuli remains controversial. While previous near-infrared spectroscopy (NIRS) studies in awake infants have demonstrated cortical activations in response to meaningful/attractive visual stimuli, functional magnetic resonance imaging (fMRI) studies performed on sleeping infants showed negative blood oxygenation level-dependent (BOLD) responses to high-luminance unpatterned stimulations, such as a photic stimulation. To examine the effect of the characteristics of visual stimuli on cortical processing in awake infants, we measured cortical hemodynamic responses in 6-month-old infants during the presentation of a high-luminance unpatterned stimulus by using a NIRS system with 94 measurement channels. Results from 35 infants showed dissociated cortical responses between the occipital region and the other parts of the cortex, including the temporal and prefrontal regions. Although the visual stimulus produced sustained increases in oxygenated hemoglobin (oxy-Hb) signals in the temporal and prefrontal regions, it produced a transient increase in oxy-Hb signals followed by a salient decrease in oxy-Hb signals during a trial in a focal region of the occipital visual region. This suggests that the deactivation of the occipital visual region in response to visual stimulation is not a phenomenon that occurs only in the sleeping state, but that a high-luminance unpatterned stimulus can induce deactivation even in the awake infants.     

癫痫发作类型与EEG的相关性

目的：分析各种发作类型癫痫及其与脑电图（EEG）表现的关系。方法：对352例确诊癫痫患者行规范的病史询问及长程EEG监测（描记时间10～15h）,并按照1981年ILAE分类和名词委员会推荐的癫痫发作的分类方案进行发作症状的分类,按照1989年II,AE推荐的癫痫和癫痫综合征的分类作出诊断,分析其发作类型和EEG之间的相关性。结果：在352例中,EEG异常246例,异常率为69．9％,24例（6．8％）记录到临床发作。EEG异常率与发作频率相关,每月发作大于4次者较每月发作少于4次者EEG异常率显著升高（P=0．014）。部分性发作和全面性发作的患者异常率比较差异无显著意义（P=0．929）,但前者更多表现为EEG局限性异常（P=0．014）。结论：规范的长程EEG检查异常率较高,EEG异常率与发作频率相关,不同癫痫发作类型患者的EEG表现有差异。     

Itch induced by a novel method leads to limbic deactivations a functional MRI study

Functional brain imaging studies on itch usually use histamine as a stimulus and, in consequence, have to cope with the highly variable time course of this particular itch sensation. In this study, we describe a novel method of histamine application. To provoke itch, a mixture of histamine and codeine was applied through intradermally positioned microdialysis fiber. The itch was terminated by lidocaine application through the same fiber. During one fMRI session, this procedure was repeated four times in four different microdialysis fibers, including one placebo control. Itch ratings of the subjects were correlated with blood-oxygen-level-dependent (BOLD) effects. In a subsequent experiment performed in the same fMRI session, heat pain was provoked in the right forearm with a Peltier thermode. During both experiments, activation clusters were found in brain areas that have been described previously to be frequently activated in response to painful stimuli. This includes prefrontal areas, supplementary motor areas (SMA), premotor cortex, anterior insula, anterior midcingulate cortex, S1, S2, thalamus, basal ganglia, and cerebellum. In general, itch stimulation entailed more activation clusters, in particular on the contralateral brain side. Only on itch, but not on heat pain, negative BOLD signals were found in the subgenual anterior cingulate cortex and the amygdala. The latter results may be associated with the itch induced urge to scratch. Amygdala deactivation may be related to the preparation of scratching by aiming to dissolve the otherwise aversive effects of the noxious scratch stimuli. These negative BOLD effects may also be attributed to the stressful character of itch stimulation.     

脑电图在大脑半球切除术前后表现及临床意义

目的:探讨半球综合征(Hemispheric syndromes,HS)患者病变半球切除术前后发作间期与发作期的脑电图(EEG)表现特点及其临床意义。方法:总结自2001年4月至2004年4月行大脑半球切除手术的4例患者的临床资料并结合脑磁共振成像(MRI),对其发作间期、发作期以及病损大脑半球切除术半年后复查EEG结果进行分析总结。结果:4例患者MRI均显示为一侧半球广泛病变,对侧正常。EEG均表现为两侧不对称,患侧波幅明显减低。其中3例EEG表现出背景抑制。发作间期癫 癎异常波表现:1例癎样放电出现的侧别与影像学检查结果相反,2例患者出现了双侧同步癎样放电,1 例无明显异常波。发作期EEG表现:1例患者癎样放电起源与病灶侧别相符,其余3例出现在病灶的对侧。所有患者均接受了病灶侧大脑半球切除术,术后随访最短1例为12个月,4例均没有癫癎发作。手术半年后复查EEG,2例患者对侧发作间期癎样放电未消失,2例对侧EEG正常。结论:EEG对HS患者手术前定位诊断及预后判断都有一定的价值。分析HS头皮EEG时,要考虑到两侧大脑结构的绝对不对称性;当出现双侧癫癎异常放电时,不排除手术可以获得良好预后的可能性,可考虑对患侧半球行切除术治疗。EEG发作期单侧起源,在HS患者癫癎灶定位方面,与MRI结果相比,价值有限。HS患者,如明确患侧已不存在重要功能,应尽早手术治疗。